How did you Raven's Home? I mean I have placed a subtle hint but didn't expect any one to figure it out that quickly. Anyway, it's not a bug. If you find her ghostpedia page you will learn how to get her to that state and can't be defeated.
I figured it out by accident. All the NPCs disappeared when I got into Raven’s Home after walking around several maps, and I thought this was a bug. Soon, I noticed that the placement of objects in the map was different than usual, and I met Liz and was sure that this wasn’t a bug. And then I started looking for things that in my memory was i triggered things, then I found a ‘sticker’ and after a few experiments I found it was a trigger :P
By the way, there’s another bug i found that catches a ghost and then quickly presses the X button while she’s still there, triggering the scene again in that state and the game breaks down.